Popped in to a watch restorer's kiosk and asked if he had any Seikos on hand. He pulled this one, Seiko 6138 -xxxx (I haven't figured out which version, there's about a dozen versions from the early 70s) and I really liked it. He opened it and it looked all original and was in very good shape and the chrono ran smoother than a 7750 so I said "wrap it up". Here's some general info on the line, it was the Seiko chrono workhorse of the 70s:

The SEIKO 6139 and 6138 series are the first fully integrated automatic chronograph in the world featuring column wheel and vertical coupling mechanism. With this movement, they have set the standard which was followed by the Swiss watch industries 20 years later. The same movement configuration was adopted by Rolex when it made its own in-house movement for Daytona in the year 2000, 30 years after SEIKO released the caliber 6139 and 6138.The 6138 was the successor of the 6139 automatic chronograph movement but produced in parallel until 1979. The 6138 was technically at least equal to his Swiss counterparts as it had a fully integrated chronograph. There were two versions of the 6138, the 6138A introduced in 1970 had 21 jewels. The 6138B was introduced a bit later with 23 jewels. Both feature a column wheel that regulates the chrono functions, and a vertical clutch mechanism for the engagement. It is still considered to be superior over the mechanically more simple Cam Actuated movements. The movement diameter measures 27,4mm and a height of 7,9mm. The "speed" is 21.600 a/H.The 6138A and B is a 2 register chronograph, counting up to 30 minutes on one subdial and another 12 hours on the second dial. The second-hand measures up to 1/6th of a second (21600 beats per hours/3600s). All 6138 movements feature a quick-set day/date indicator and they can be handwound, something that people often miss on most other Seiko 6139 automatic movements.Compared to Zenith’s El Primero, both the 6139 and 6138 have no separate second-hand which means with the chrono functions disabled there is nothing moving on the dial. Generally, the 6138 movements are considered as very reliable and need a minimum of service. I have seen many 6138 watches running within the Chronometer norm which is a notable fact for watches being 40 years old.